<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style type="text/css">
      canvas {
          background-color: #cccccc;
          border: 1px solid black;
      }
  </style>

</head>
<body>
  <canvas class="learn_canvas" id="myCanvas" width="600" height="600"></canvas>
  <script>
    // function draw() {
    //   var canvas = document.getElementById('myCanvas');
    //   if(!canvas.getContext) return;
    //   var ctx = canvas.getContext('2d');
    //   ctx.fillStyle = "white";
    //   ctx.translate(0, Math.sin(0.03) * 4)
    //   ctx.arc(275,75,50,0,2*Math.PI);
    //   ctx.fill();
    //   ctx.closePath();
    // }
    // draw();
    var sun = new Image();
    var moon = new Image();
    var earth = new Image();
    function init(){
      sun.src = 'https://mdn.mozillademos.org/files/1456/Canvas_sun.png';
      moon.src = 'https://mdn.mozillademos.org/files/1443/Canvas_moon.png';
      earth.src = 'https://mdn.mozillademos.org/files/1429/Canvas_earth.png';
      window.requestAnimationFrame(draw);
    }

    function draw() {
      var ctx = document.getElementById('myCanvas').getContext('2d');

      ctx.globalCompositeOperation = 'destination-over';
      ctx.clearRect(0,0,300,300); // clear canvas

      ctx.fillStyle = 'rgba(0,0,0,0.4)';
      ctx.strokeStyle = 'rgba(0,153,255,0.4)';
      ctx.save();
      ctx.translate(150,150);

      // Earth
      var time = new Date();
      ctx.rotate( ((2*Math.PI)/60)*time.getSeconds() + ((2*Math.PI)/60000)*time.getMilliseconds() );
      ctx.translate(105,0);
      ctx.drawImage(earth,-12,-12);

      // Moon
      ctx.save();
      ctx.rotate( ((2*Math.PI)/6)*time.getSeconds() + ((2*Math.PI)/6000)*time.getMilliseconds() );
      ctx.translate(0,28.5);
      ctx.drawImage(moon,-3.5,-3.5);
      ctx.restore();

      ctx.restore();
      
      ctx.beginPath();
      ctx.arc(150,150,105,0,Math.PI*2,false); // Earth orbit
      ctx.stroke();
    
      ctx.drawImage(sun,0,0,300,300);

      window.requestAnimationFrame(draw);
    }

    init();
  </script>
</body>
</html>